Retaining Lag value for next rows calculation

[Timzactive]

New here so I'd really appreciate any help I can get.

So I have loan data which is already sorted by lender, I.D. and date_taken.  First, for all count=1 the newest date(created var) = date_paid.  Then I want the code to look at the lagged value(of the new variable(newest date)) to see if it is greater than the current date paid on the loan.  If it is, I want the larger date in the new variable's observation.  This new variable's value should then be looked at to calculate the next observations value.  Below is an example of what IT SHOULD LOOK LIKE and the Right most column is what I actually get. Followed by the current code I am running.

Lender	I.D	Count	Date Loan Taken	Date Paid	Newest Date(correct)	Newest Date(actual)
POP	554	1	5/15/2013	6/12/2013	6/12/2013	6/12/2013
POP	554	2	5/30/2013	6/30/2014	6/30/2014	6/30/2014
POP	554	3	6/20/2013	6/15/2013	6/30/2014	6/15/2013
POP	554	4	7/30/2013	6/30/2013	6/30/2014	6/30/2013
POP	788	1	12/10/2012	2/15/2013	2/15/2013	2/15/2013
POP	788	2	12/25/2012	2/27/2013	2/27/2013	2/27/2013

data input.loan_sequence_count_2;

  set input.loan_sequence_count_1;

     Newest_Date=. ;

run;

data input.loan_sequence_count_3;

  set input.loan_sequence_count_2;

  by lender ID;

  if first.Newest_Date then Newest_Date= Date_Paid;

  else do;

  if Date_Paid> lag(Newest_Date) then Newest_Date= Date_Paid;

  else Newest_Date= lag(Newest_Date);

  retain Newest_Date;

  end;

run;

Now I know that the lag function won't work here except for the second observation of a group.  So I am curious if there is a two step process I can do or something else I haven't thought of to look at the subsequent lag values when creating a new value.

Thanks,

Tim

[Reeza]

UNTESTED:

Data Want;

Set Have;

BY lender id;

retain latest_date;

if first.id then latest_date=date_paid;

else latest_date=max(date_paid, latest_date);

run;

[Timzactive]

^^^This earlier thread answers my question perfectly with a by statement.  Thanks for your help.